RFID reader system capable of adjusting tags to modify internal operations for a sensed environment

ABSTRACT

A method of adjusting operation of an RFID tag for an environment is described. The method includes sensing an aspect of the environment. The method also includes sending an instruction, based on the sensed aspect of the environment, to the RFID tag. The instruction encoded in a TUNE command. The instruction causes the RFID tag to perform a specific act. The specific act includes one of the following: turning a sub-circuit of the RFID tag&#39;s semiconductor chip on; turning a sub-circuit of the RFID tag&#39;s semiconductor chip off; altering a bias current within a sub-circuit of the RFID tag&#39;s semiconductor chip; altering a bias voltage within a sub-circuit of the RFID tag&#39;s semiconductor chip; and, adjusting a threshold within a sub-circuit of the RFID tag&#39;s semiconductor chip.

CLAIM OF PRIORITY

The present application claims priority to and the benefit of the filingdate of U.S. Provisional Application Ser. No. 61/028,644 filed on Feb.14, 2008.

FIELD OF INVENTION

The present description addresses the field of Radio FrequencyIDentification (RFID) systems, and more specifically to an RFID readersystem capable of adjusting tags to modify internal operations for asensed environment.

BACKGROUND

Radio Frequency IDentification (RFID) systems typically include RFIDtags and RFID readers. RFID readers are also known as RFIDreader/writers or RFID interrogators. RFID systems can be used in manyways for locating and identifying objects to which the tags areattached. RFID systems are particularly useful in product-related andservice-related industries for tracking objects being processed,inventoried, or handled. In such cases, an RFID tag is usually attachedto an individual item, or to its package.

In principle, RFID techniques entail using an RFID reader to interrogateone or more RFID tags. The reader transmitting a Radio Frequency (RF)wave performs the interrogation. The RF wave is typicallyelectromagnetic, at least in the far field. The RF wave can also bepredominantly electric or magnetic in the near field. The RF wave mayencode one or more commands that instruct the tags to perform one ormore actions.

A tag that senses the interrogating RF wave responds by transmittingback another RF wave. The tag generates the transmitted back RF waveeither originally, or by reflecting back a portion of the interrogatingRF wave in a process known as backscatter. Backscatter may take place ina number of ways.

The reflected-back RF wave may further encode data stored internally inthe tag, such as a number. The response is demodulated and decoded bythe reader, which thereby identifies, counts, or otherwise interactswith the associated item. The decoded data can denote a serial number, aprice, a date, a destination, other attribute(s), any combination ofattributes, and so on. Accordingly, when a reader reads a tag code, datacan be learned about the associated item that hosts the tag, and/orabout the tag itself.

An RFID tag typically includes an antenna system, a radio section, apower management section, an oscillator, and frequently a logicalsection, a memory, or both. In earlier RFID tags, the power managementsection included an energy storage device, such as a battery. RFID tagswith a battery are known as active or semi-active tags. Advances insemiconductor technology have miniaturized the electronics so much thatan RFID tag can be powered solely by the RF signal it receives. SuchRFID tags do not include a battery, and are called passive tags.

A well-known problem in RFID systems is expedience in reading the tags,especially where it is desired to read more than one of the codes storedin each tag. The problem becomes exacerbated if there are many tags, orthe host items are moving and thus allow only limited time to read theirtags.

SUMMARY

A method of adjusting operation of an RFID tag for an environment isdescribed. The method includes sensing an aspect of the environment. Themethod also includes sending an instruction, based on the sensed aspectof the environment, to the RFID tag. The instruction encoded in a TUNEcommand. The instruction causes the RFID tag to perform a specific act.The specific act includes one of the following: turning a sub-circuit ofthe RFID tag's semiconductor chip on; turning a sub-circuit of the RFIDtag's semiconductor chip off; altering a bias current within asub-circuit of the RFID tag's semiconductor chip; altering a biasvoltage within a sub-circuit of the RFID tag's semiconductor chip; and,adjusting a threshold within a sub-circuit of the RFID tag'ssemiconductor chip.

BRIEF DESCRIPTION OF THE DRAWINGS

The following Detailed Description proceeds with reference to theaccompanying Drawings, in which:

FIG. 1 is a block diagram of components of an RFID system.

FIG. 2 is a diagram showing components of a passive RFID tag, such as atag that can be used in the system of FIG. 1.

FIG. 3 is a conceptual diagram for explaining a half-duplex mode ofcommunication between the components of the RFID system of FIG. 1.

FIG. 4 is a block diagram showing a detail of an RFID reader system,such as the one shown in FIG. 1.

FIG. 5 is a block diagram of a whole RFID reader system according toembodiments.

FIG. 6 is a block diagram illustrating an overall architecture of anRFID reader system according to embodiments.

FIG. 7 is a diagram illustrating an environment of RFID tags, a sensorthat senses the environment, and, an RFID reader that communicates withthe RFID tags.

FIG. 8 is a flowchart illustrating a method that may be performed by thesystem of FIG. 7.

FIG. 9A is a diagram illustrating a first embodiment of an RFID tagsemiconductor chip that is capable of receiving and performing aninstruction to perform a specific act on a sub-circuit of thesemiconductor chip.

FIG. 9B is a diagram illustrating a second embodiment of an RFID tagsemiconductor chip that is capable of receiving and performing aninstruction to perform a specific act on a sub-circuit of thesemiconductor chip.

FIG. 9C is a diagram illustrating a third embodiment showing differentsub-circuits whose operation may be adjusted based on a sensed aspect ofan environment.

FIG. 10A is a table illustrating the fields of the Select command of theGen2 Spec version 1.1.0, versions of which may be used as any one ormore of the commands from an RFID reader system component according toembodiments.

FIG. 10B is a table illustrating how a number of custom commands can beenabled in a reader and a tag.

FIG. 10C is a table showing sample values that can be used for the tableof FIG. 10B.

DETAILED DESCRIPTION

The present invention is now described in more detail. While it isdisclosed in its preferred form, the specific embodiments of theinvention as disclosed herein and illustrated in the drawings are not tobe considered in a limiting sense. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Indeed, it should be readily apparent in view of the present descriptionthat the invention may be modified in numerous ways. Among other things,the present invention may be embodied as devices, methods, software, andso on. Accordingly, the present invention may take the form of anentirely hardware embodiment, an entirely software embodiment, anentirely firmware embodiment, or an embodiment combining aspects of theabove. This description is, therefore, not to be taken in a limitingsense.

FIG. 1 is a diagram of components of a typical RFID system 100,incorporating aspects of the invention. An RFID reader 110 transmits aninterrogating Radio Frequency (RF) wave 112. RFID tag 120 in thevicinity of RFID reader 110 may sense interrogating RF wave 112, andgenerate wave 126 in response. RFID reader 110 senses and interpretswave 126.

Reader 110 and tag 120 exchange data via wave 112 and wave 126. In asession of such an exchange each encodes, modulates, and transmits datato the other, and each receives, demodulates, and decodes data from theother. The data is modulated onto, and demodulated from, RF waveforms.

Encoding the data in waveforms can be performed in a number of differentways. For example, protocols are devised to communicate in terms ofsymbols, also called RFID symbols. A symbol for communicating can be adelimiter, a calibration symbol, and so on. Further symbols can beimplemented for ultimately exchanging binary data, such as “0” and “1”,if that is desired. In turn, when the waveforms are processed internallyby reader 110 and tag 120, they can be equivalently considered andtreated as numbers having corresponding values, and so on.

Tag 120 can be passive or semi-active or active, i.e. having its ownpower source. Where tag 120 is a passive tag, it is powered from wave112.

FIG. 2 is a diagram of an RFID tag 220, which can be the same as tag 120of FIG. 1. Tag 220 is implemented as a passive tag, meaning it does nothave its own power source. Much of what is described in this document,however, applies also to active tags.

Tag 220 is formed on a substantially planar inlay 222, which can be madein many ways known in the art. Tag 220 includes an electrical circuit,which is preferably implemented in an integrated circuit (IC) 224. IC224 is arranged on inlay 222.

Tag 220 also includes an antenna for exchanging wireless signals withits environment. The antenna is usually flat and attached to inlay 222.IC 224 is electrically coupled to the antenna via suitable antenna ports(not shown in FIG. 2).

The antenna may be made in a number of ways, as is well known in theart. In the example of FIG. 2, the antenna is made from two distinctantenna segments 227, which are shown here forming a dipole. Many otherembodiments are possible, using any number of antenna segments.

In some embodiments, an antenna can be made with even a single segment.Different points of the segment can be coupled to one or more of theantenna ports of IC 224. For example, the antenna can form a singleloop, with its ends coupled to the ports. It should be remembered that,when the single segment has more complex shapes, even a single segmentcould behave like multiple segments, at the frequencies of RFID wirelesscommunication.

In operation, a signal is received by the antenna, and communicated toIC 224. IC 224 both harvests power, and responds if appropriate, basedon the incoming signal and its internal state. In order to respond byreplying, IC 224 modulates the reflectance of the antenna, whichgenerates the backscatter from a wave transmitted by the reader.Coupling together and uncoupling the antenna ports of IC 224 canmodulate the reflectance, as can a variety of other means.

In the embodiment of FIG. 2, antenna segments 227 are separate from IC224. In other embodiments, antenna segments may alternately be formed onIC 224, and so on.

The components of the RFID system of FIG. 1 may communicate with eachother in any number of modes. One such mode is called full duplex.Another such mode is called half-duplex, and is described below.

FIG. 3 is a conceptual diagram 300 for explaining the half-duplex modeof communication between the components of the RFID system of FIG. 1,especially when tag 120 is implemented as passive tag 220 of FIG. 2. Theexplanation is made with reference to a TIME axis, and also to a humanmetaphor of “talking” and “listening”. The actual technicalimplementations for “talking” and “listening” are now described.

RFID reader 110 and RFID tag 120 talk and listen to each other by takingturns. As seen on axis TIME, when reader 110 talks to tag 120 thecommunication session is designated as “R→T”, and when tag 120 talks toreader 110 the communication session is designated as “T→R”. Along theTIME axis, a sample R→T communication session occurs during a timeinterval 312, and a following sample T→R communication session occursduring a time interval 326. Of course interval 312 is typically of adifferent duration than interval 326—here the durations are shownapproximately equal only for purposes of illustration.

According to blocks 332 and 336, RFID reader 110 talks during interval312, and listens during interval 326. According to blocks 342 and 346,RFID tag 120 listens while reader 110 talks (during interval 312), andtalks while reader 110 listens (during interval 326).

In terms of actual technical behavior, during interval 312, reader 110talks to tag 120 as follows. According to block 352, reader 110transmits wave 112, which was first described in FIG. 1. At the sametime, according to block 362, tag 120 receives wave 112 and processesit, to extract data and so on. Meanwhile, according to block 372, tag120 does not backscatter with its antenna, and according to block 382,reader 110 has no wave to receive from tag 120.

During interval 326, tag 120 talks to reader 110 as follows. Accordingto block 356, reader 110 transmits a Continuous Wave (CW), which can bethought of as a carrier signal that ideally encodes no information. Asdiscussed before, this carrier signal serves both to be harvested by tag120 for its own internal power needs, and also as a wave that tag 120can backscatter. Indeed, during interval 326, according to block 366,tag 120 does not receive a signal for processing. Instead, according toblock 376, tag 120 modulates the CW emitted according to block 356, soas to generate backscatter wave 126. Concurrently, according to block386, reader 110 receives backscatter wave 126 and processes it.

In the above, an RFID reader/interrogator may communicate with one ormore RFID tags in any number of ways. Some such ways are described inprotocols. A protocol is a specification that calls for specific mannersof signaling between the reader and the tags.

One such protocol is called the Specification for RFID Air Interface—EPC(TM) Radio-Frequency Identity Protocols Class-1 Generation-2 UHF RFIDProtocol for Communications at 860 MHz-960 MHz, which is alsocolloquially known as “the Gen2 Spec”. The Gen2 Spec has been ratifiedby EPCglobal, which is an organization that maintains a website at:<http://www.epcglobalinc.org/> at the time this document is initiallyfiled with the USPTO. Version 1.1.0 of the Gen2 Spec is herebyincorporated by reference in its entirety.

In addition, a protocol can be a variant of a stated specification suchas the Gen2 Spec, for example including fewer or additional commandsthan the stated specification calls for, and so on. In such instances,additional commands are sometimes called custom commands.

FIG. 4 is a block diagram showing a detail of an RFID reader system 410,which can be the same as reader 110 shown in FIG. 1. A unit 420 is alsoknown as a box 420, and has one or more antenna drivers 430. In someembodiments it has four drivers 430. For each driver 430 there is anoutput connector. The output connector is typically for a coaxial cable.Accordingly, connectors 435 can be attached to the outputs of theprovided respective drivers 430, and then connectors 435 can be attachedto respective antennas 440.

A driver 430 can send to its respective antenna 440 a driving signalthat is in the RF range, which is why connector 435 is typically but notnecessarily a coaxial cable. The driving signal causes the antenna 440to transmit an RF wave 412, which is analogous to RF wave 112 of FIG. 1.In addition, RF wave 426 can be backscattered from the RFID tags,analogous to RF wave 126 of FIG. 1. Backscattered RF wave 426 isreceived by an antenna 440 and ultimately becomes a signal sensed byunit 420.

Unit 420 also has other components 450, such as hardware and/or softwareand/or firmware, which may be described in more detail later in thisdocument. Components 450 control drivers 430, and as such cause RF wave412 to be transmitted, and the sensed backscattered RF wave 426 to beinterpreted. Optionally and preferably there is a communication link 425to other equipment, such as computers and the like, for remote operationof system 410.

FIG. 5 is a block diagram of a whole RFID reader system 500 according toembodiments. System 500 includes a local block 510, and optionallyremote components 570. Local block 510 and remote components 570 can beimplemented in any number of ways. It will be recognized that reader 110of FIG. 1 is the same as local block 510, if remote components 570 arenot provided. Alternately, reader 110 can be implemented instead bysystem 500, of which only the local block 510 is shown in FIG. 1. Plus,local block 510 can be unit 420 of FIG. 4.

Local block 510 is responsible for communicating with the tags. Localblock 510 includes a block 551 of an antenna and a driver of the antennafor communicating with the tags. Some readers, like that shown in localblock 510, contain a single antenna and driver. Some readers containmultiple antennas and drivers and a method to switch signals among them,including sometimes using different antennas for transmitting and forreceiving. And some readers contain multiple antennas and drivers thatcan operate simultaneously. A demodulator/decoder block 553 demodulatesand decodes backscattered waves received from the tags via antenna block551. Modulator/encoder block 554 encodes and modulates an RF wave thatis to be transmitted to the tags via antenna block 551.

Local block 510 additionally includes an optional local processor 556.Processor 556 may be implemented in any number of ways known in the art.Such ways include, by way of examples and not of limitation, digitaland/or analog processors such as microprocessors and digital-signalprocessors (DSPs); controllers such as microcontrollers; softwarerunning in a machine such as a general purpose computer; programmablecircuits such as Field Programmable Gate Arrays (FPGAs),Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices(PLDs), Application Specific Integrated Circuits (ASIC), any combinationof one or more of these; and so on. In some cases some or all of thedecoding function in block 553, the encoding function in block 554, orboth, may be performed instead by processor 556.

Local block 510 additionally includes an optional local memory 557.Memory 557 may be implemented in any number of ways known in the art.Such ways include, by way of examples and not of limitation, nonvolatilememories (NVM), read-only memories (ROM), random access memories (RAM),any combination of one or more of these, and so on. Memory 557, ifprovided, can include programs for processor 556 to run, if provided.

In some embodiments, memory 557 stores data read from tags, or data tobe written to tags, such as Electronic Product Codes (EPCs), TagIdentifiers (TIDs) and other data. Memory 557 can also include referencedata that is to be compared to the EPC codes, instructions and/or rulesfor how to encode commands for the tags, modes for controlling antenna551, and so on. In some of these embodiments, local memory 557 isprovided as a database.

Some components of local block 510 typically treat the data as analog,such as the antenna/driver block 551. Other components such as memory557 typically treat the data as digital. At some point there is aconversion between analog and digital. Based on where this conversionoccurs, a whole reader may be characterized as “analog” or “digital”,but most readers contain a mix of analog and digital functionality.

If remote components 570 are indeed provided, they are coupled to localblock 510 via an electronic communications network 580. Network 580 canbe a Local Area Network (LAN), a Metropolitan Area Network (MAN), a WideArea Network (WAN), a network of networks such as the internet, or amere local communication link, such as a USB, PCI, and so on. In turn,local block 510 then includes a local network connection 559 forcommunicating with network 580.

There can be one or more remote component(s) 570. If more than one, theycan be located at the same location, or in different locations. They canaccess each other and local block 510 via network 580, or via othersimilar networks, and so on. Accordingly, remote component(s) 570 canuse respective remote network connections. Only one such remote networkconnection 579 is shown, which is similar to local network connection559, etc.

Remote component(s) 570 can also include a remote processor 576.Processor 576 can be made in any way known in the art, such as wasdescribed with reference to local processor 556.

Remote component(s) 570 can also include a remote memory 577. Memory 577can be made in any way known in the art, such as was described withreference to local memory 557. Memory 577 may include a local database,and a different database of a Standards Organization, such as one thatcan reference EPCs.

Of the above-described elements, it is advantageous to consider acombination of these components, designated as operational processingblock 590. Block 590 includes those that are provided of the following:local processor 556, remote processor 576, local network connection 559,remote network connection 579, and by extension an applicable portion ofnetwork 580 that links connection 559 with connection 579. The portioncan be dynamically changeable, etc. In addition, block 590 can receiveand decode RF waves received via antenna 551, and cause antenna 551 totransmit RF waves according to what it has processed.

Block 590 includes either local processor 556, or remote processor 576,or both. If both are provided, remote processor 576 can be made suchthat it operates in a way complementary with that of local processor556. In fact, the two can cooperate. It will be appreciated that block590, as defined this way, is in communication with both local memory 557and remote memory 577, if both are present.

Accordingly, block 590 is location agnostic, in that its functions canbe implemented either by local processor 556, or by remote processor576, or by a combination of both. Some of these functions are preferablyimplemented by local processor 556, and some by remote processor 576.Block 590 accesses local memory 557, or remote memory 577, or both forstoring and/or retrieving data.

Reader system 500 operates by block 590 generating communications forRFID tags. These communications are ultimately transmitted by antennablock 551, with modulator/encoder block 554 encoding and modulating theinformation on an RF wave. Then data is received from the tags viaantenna block 551, demodulated and decoded by demodulator/decoder block553, and processed by processing block 590.

The invention additionally includes programs, and methods of operationof the programs. A program is generally defined as a group of steps oroperations leading to a desired result, due to the nature of theelements in the steps and their sequence. A program is usuallyadvantageously implemented as a sequence of steps or operations for aprocessor, such as the structures described above.

Performing the steps, instructions, or operations of a program requiresmanipulation of physical quantities. Usually, though not necessarily,these quantities may be transferred, combined, compared, and otherwisemanipulated or processed according to the steps or instructions, andthey may also be stored in a computer-readable medium. These quantitiesinclude, for example, electrical, magnetic, and electromagnetic chargesor particles, states of matter, and in the more general case can includethe states of any physical devices or elements. It is convenient attimes, principally for reasons of common usage, to refer to informationrepresented by the states of these quantities as bits, data bits,samples, values, symbols, characters, terms, numbers, or the like. Itshould be borne in mind, however, that all of these and similar termsare associated with the appropriate physical quantities, and that theseterms are merely convenient labels applied to these physical quantities,individually or in groups.

The invention furthermore includes storage media. Such media,individually or in combination with others, have stored thereoninstructions of a program made according to the invention. A storagemedium according to the invention is a computer-readable medium, such asa memory, and is read by a processor of the type mentioned above. If amemory, it can be implemented in a number of ways, such as Read OnlyMemory (ROM), Random Access Memory (RAM), etc., some of which arevolatile and some non-volatile.

Even though it is said that the program may be stored in acomputer-readable medium, it should be clear to a person skilled in theart that it need not be a single memory, or even a single machine.Various portions, modules or features of it may reside in separatememories, or even separate machines. The separate machines may beconnected directly, or through a network such as a local access network(LAN) or a global network such as the Internet.

Often, for the sake of convenience only, it is desirable to implementand describe a program as software. The software can be unitary, orthought in terms of various interconnected distinct software modules.

This detailed description is presented largely in terms of flowcharts,algorithms, and symbolic representations of operations on data bits onand/or within at least one medium that allows computational operations,such as a computer with memory. Indeed, such descriptions andrepresentations are the type of convenient labels used by those skilledin programming and/or the data-processing arts to effectively convey thesubstance of their work to others skilled in the art. A person skilledin the art of programming may use these descriptions to readily generatespecific instructions for implementing a program according to thepresent invention.

Embodiments of an RFID reader system can be implemented as hardware,software, firmware, or any combination. It is advantageous to considersuch a system as subdivided into components or modules. A person skilledin the art will recognize that some of these components or modules canbe implemented as hardware, some as software, some as firmware, and someas a combination. An example of such a subdivision is now described.

FIG. 6 is a block diagram illustrating an overall architecture of anRFID reader system 600 according to embodiments. It will be appreciatedthat system 600 is considered subdivided into modules or components.Each of these modules may be implemented by itself, or in combinationwith others. It will be recognized that some aspects are parallel withthose of FIG. 5. In addition, some of them may be present more thanonce.

RFID reader system 600 includes one or more antennas 610, and an RFFront End 620, for interfacing with antenna(s) 610. These can be made asdescribed above. In addition, Front End 620 typically includes analogcomponents.

System 600 also includes a Signal Processing module 630. In thisembodiment, module 630 exchanges waveforms with Front End 620, such as Iand Q waveform pairs. In some embodiments, signal processing module 630is implemented by itself in an FPGA.

System 600 also includes a Physical Driver module 640, which is alsoknown as Data Link. In this embodiment, module 640 exchanges bits withmodule 630. Data Link 640 can be the stage associated with framing ofdata. In one embodiment, module 640 is implemented by a Digital SignalProcessor.

System 600 additionally includes a Media Access Control module 650,which is also known as MAC layer. In this embodiment, module 650exchanges packets of bits with module 640. MAC layer 650 can be thestage for making decisions for sharing the medium of wirelesscommunication, which in this case is the air interface. Sharing can bebetween reader system 600 and tags, or between system 600 with anotherreader, or between tags, or a combination. In one embodiment, module 650is implemented by a Digital Signal Processor.

System 600 moreover includes an Application Programming Interface module660, which is also known as API, Modem API, and MAPI. In someembodiments, module 660 is itself an interface for a user.

All of these functionalities can be supported by one or more processors.One of these processors can be considered a host processor. Such aprocessor would, for example, exchange signals with MAC layer 650 viamodule 660. In some embodiments, the processor can include applicationsfor system 600. In some embodiments, the processor is not considered asa separate module, but one that includes some of the above-mentionedmodules of system 600.

A user interface 680 may be coupled to API 660. User interface 680 canbe manual, automatic, or both. It can be supported by a separateprocessor than the above mentioned processor, or implemented on it.

It will be observed that the modules of system 600 form something of achain. Adjacent modules in the chain can be coupled by the appropriateinstrumentalities for exchanging signals. These instrumentalitiesinclude conductors, buses, interfaces, and so on. Theseinstrumentalities can be local, e.g. to connect modules that arephysically close to each other, or over a network, for remotecommunication.

The chain is used in opposite directions for receiving and transmitting.In a receiving mode, wireless waves are received by antenna(s) 610 assignals, which are in turn processed successively by the various modulesin the chain. Processing can terminate in any one of the modules. In atransmitting mode, initiation can be in any one of these modules.Ultimately, signals are routed internally, for antenna(s) 610 totransmit as wireless waves.

The architecture of system 600 is presented for purposes of explanation,and not of limitation. Its particular subdivision into modules need notbe followed for creating embodiments according to the invention.Furthermore, the features of the invention can be performed eitherwithin a single one of the modules, or by a combination of them.

FIG. 7 shows an improved RFID reader system having a sensor 704 thatsenses an aspect of an environment 701 in which one or more RFID tags703 reside. In an embodiment, the sensed aspect is recognized by an RFIDreader 702 which subsequently determines an instruction for one or moreof the tags 703 based on the sensed aspect. The RFID reader 702 thensends the instruction to the tag(s) 703. The processing of theinstruction by the tag(s) adjusts the tag(s) for the environment 701.For instance, if the environment is sensed to be electromagnetically“noisy”, the instruction can instruct the tag(s) to turn on one or morecircuits to reduce the communication error rate. Other examples of thekinds of adjustments that may be made are described in more detailfurther below.

The sensing of an environment, determining of an appropriate instructionfor that environment, and sending of the instruction to one or more tagsmay be performed in various ways. For instance, according to oneembodiment, the sensor 704 is integrated with the RFID reader 702. Thatis, the sensor can be viewed as a component of the reader 702.

In alternate embodiments, the sensor 704 may be associated with anotherdevice other than the reader 702. For instance, the sensor 704 may beintegrated with a computer and/or controller (not shown in FIG. 7) thatis communicatively coupled to the reader 702 through a network. In oneaspect of this approach, the computer and/or controller cause the sensedenvironmental aspect to be sent to the reader 702 through the network.In this case, the reader 702 determines the instruction and sends theinstruction to the tag(s) 703. In another approach, the computer and/orcontroller determines an appropriate instruction and forwards it to thereader 702 (which forwards it to the tag(s)). In yet another approach,the sensed aspect is sent to another machine (such as another computerand/or controller) that determines the appropriate instruction for thetag(s). The machine then identifies the instruction to the reader 702(e.g., by sending the instruction to the reader 702 over a network) andthe reader 702 sends the instruction to the tag(s) 703. Here, theseparate computer/controller/machine may be a reader controller thatcontrols reader 702.

Various aspects of the environment 701 can be sensed. For instance, anyone or more of the following can be sensed: 1) the electromagnetic noisewithin the environment; 2) the presence and/or the number of RFIDreaders within the environment; 3) the humidity within the environment;4) the temperature within the environment; and, 5) the environment'selectromagnetic reflection properties. Correspondingly, sensor 704includes some kind of environmental sensor such as a receiver to sensenoise, other readers and/or electromagnetic reflection properties of theenvironment. Sensor 704 may also include a humidity detector and/or atemperature detector.

Generally, the above environmental aspects have some bearing on therelative difficulty of a tag to successfully receive information,transmit information and/or perform internal operations. Generally,higher electromagnetic noise (e.g., from various transmitters thattransmit into the environment 701), a larger number of readers, higherhumidity (which causes the wireless transmission medium of theenvironment to become more “lossy”), higher temperature, and greaterreflected electromagnetic energy within the environment causecommunication between the reader 702 and the tag(s) 703 to become moredifficult and/or challenging.

Appropriate tag adjustments for such difficult/challenging environmentalconditions may include: 1) increasing or decreasing tag oscillatorfrequency (depending on the nature of the environmental condition); 2)changing the demodulation receive path from a single modulation scheme(in which one demodulator is used) to a dual demodulation scheme (inwhich two demodulators are used); 3) enabling a random generator (e.g.,to increase available tag IDs); 4) increasing the power supply voltageon the tag, for instance, by increasing the efficiency of the tag'sconversion of received electromagnetic energy into a power supplyvoltage (e.g., by enabling or increasing the efficiency of a rectifiercircuit on the tag); 5) increasing the power supply voltage to specifictag sub-circuits (such as the tag's demodulators and/or modulator).

Other sensed environmental aspects that could warrant an operationaladjustment to one or more tags may include: 1) the expected number oftags in the environment 701; and, 2) the velocity of a tag within theenvironment 701. In the case of the former, an increasing number of tagsmay signal a need for an increase in randomness (e.g., to increase thefield of available tag ID values) and/or a need forencryption/decryption (e.g., to enable security features) and/or a needfor an increase in the amount of available memory space on the tag. Assuch, if faced with a large number of tags, an appropriate tagadjustment may be to enable a random number generator (digital oranalog), enable encryption/decryption logic and/or enable one or more ofthe tag's non volatile memory banks.

In the case of tag velocity, a tag may pass through the environment 701“quickly”. As such, in order to promote effective communication betweenthe tag and reader 702 while the tag is within the environment 701, anappropriate tag adjustment may be to increase the speed of operation ofthe tag by, for example, increasing the supply voltage on the tag,increasing the frequency of the tag's oscillator and/or increasing theread and/or write times of a non volatile memory bank that resides onthe tag. The later may be accomplished, for example, by increasing thegain of a charge pump circuit within the memory's write circuitry,and/or, increasing the gain of a sense amplifier within the memory'sread circuitry.

In one embodiment, the number of tags and/or tag velocity are not sensedby a sensor—but rather—are “sensed” by being provided as an explicitinput parameter (e.g., by a user or controller) that separatelydetermines an appropriate value.

It is worthwhile to note that the reverse of everything said above isalso largely (if not entirely) applicable. That is, for example, adecrease in the electrical noisiness and/or temperature of theenvironment may prompt tag oscillator frequency to be increased ordecreased, demodulation scheme to be switched from dual mode to singlemode, supply voltage to be lowered, etc Likewise, a decrease in thenumber of readers/tags may prompt a tag's random generator,encryption/decryption and/or memory bank sub-circuits to be disabled. Itis believed that the complete set of possibilities is so large that allof them cannot reasonably be described in the present specification. Itis nevertheless believed, however, that given a specific environmentthose of ordinary skill will be able to readily ascertain an appropriateset of tag adjustments.

FIG. 8 shows an embodiment of a methodology 800 that may be performed bythe reader system(s) discussed above. According to the methodology ofFIG. 8, an aspect of the environment is sensed 801. Then, an instructionthat is based on the sensed aspect is sent to one or more tags 802. Theinstruction is to cause the one or more tags to perform a specific act.As observed in FIG. 8, the specific act may include at least one of: i)turning a tag sub-circuit on; ii) turning a tag sub-circuit off; iii)altering a voltage bias of a tag sub-circuit; iv) altering a currentbias of a tag sub-circuit; and, v) altering a threshold of a tagsub-circuit. Here, a tag sub-circuit is generally some identifiable subportion of the tag's circuitry such as one or more of the following: arandom number generator circuit; a demodulator or demodulator receivepath circuit; a nonvolatile memory bank circuit; a modulator circuit; anencryption/decryption circuit; an oscillator circuit; a sense amplifiercircuit; a rectifier circuit; and a charge pump circuit. The instructionthat is sent to the tag may thus command the tag to turn on/off, alter avoltage and/or current bias of, and/or, alter a threshold of one or morespecific tag sub-circuits.

In one embodiment, the instruction is formatted according to a Tunecommand format. Tune command formatting is discussed in more detailfurther below. After the one or more tags receive the instruction, theinstruction is executed by the tag(s) to effect the adjustment 803. Theimmediately following discussion provides more specific detailspertaining to the design of a tag to receive and put into effect areceived instruction as described above.

FIG. 9A is a block diagram of an electrical circuit 924 according toembodiments. Circuit 924 may be formed in an IC of an RFID tag, such asIC 224 of FIG. 2. Circuit 924 has a number of main components that aredescribed in this document. Circuit 924 may have a number of additionalcomponents from what is shown and described, or different components,depending on the exact implementation.

Circuit 924 includes at least two antenna connections 932, 933, whichare suitable for coupling to one or more antenna segments (not shown inFIG. 9A). Antenna connections 932, 933 may be made in any suitable way,such as using pads and so on. In a number of embodiments more than twoantenna connections are used, especially in embodiments where moreantenna segments are used.

Circuit 924 includes a section 935. Section 935 may be implemented asshown, for example as a group of nodes for proper routing of signals. Insome embodiments, section 935 may be implemented otherwise, for exampleto include a receive/transmit switch that can route a signal, and so on.

Circuit 924 also includes a Power Management Unit (PMU) 941. PMU 941 maybe implemented in any way known in the art, for harvesting raw RF powerreceived via antenna connections 932, 933. In some embodiments, PMU 941includes at least one rectifier, and so on.

In operation, an RF wave received via antenna connections 932, 933 isreceived by PMU 941, which in turn generates power for components ofcircuit 924. This is true for either or both reader-to-tag (R→T) andtag-to-reader (T→R) communication, whether or not the received RF waveis modulated.

Circuit 924 additionally includes a demodulator 942. Demodulator 942demodulates an RF signal received via antenna connections 932, 933.Demodulator 942 may be implemented in any way known in the art, forexample including an attenuator stage, an amplifier stage, and so on.

Circuit 924 further includes a processing block 944. Processing block944 receives the demodulated signal from demodulator 942, and mayperform operations. In addition, it may generate an output signal fortransmission.

Processing block 944 may be implemented in any way known in the art. Forexample, processing block 944 may include a number of components, suchas a processor, memory, a decoder, an encoder, a state machine, and soon.

Circuit 924 additionally includes a modulator 946. Modulator 946modulates an output signal generated by processing block 944. Themodulated signal is transmitted by driving antenna connections 932, 933,and therefore driving the load presented by the coupled antenna segmentor segments. Modulator 946 may be implemented in any way known in theart, for example including a driver stage, amplifier stage, and so on.

In one embodiment, demodulator 942 and modulator 946 may be combined ina single transceiver circuit. In another embodiment, modulator 946 mayinclude a backscatter transmitter or an active transmitter. In yet otherembodiments, demodulator 942 and modulator 946 are part of processingblock 944.

Circuit 924 additionally includes a memory 950, which stores data.Memory 950 is preferably implemented as a Nonvolatile Memory (NVM),which means that the stored data is retained even when circuit 924 doesnot have power, as is frequently the case for a passive RFID tag.

FIG. 9A also shows additional circuit structures that support theexecution of an instruction aimed at changing the operation of one ormore of the tag's sub-circuits so that the tag can be adjusted for itsenvironment as discussed above with respect to FIGS. 7 and 8.Specifically, FIG. 9A shows control signal lines 960, 970, 980, 990respectively flowing to the demodulator 942, PMU 941, modulator 946, andmemory 950 sub-circuits. Note that memory 950 may be composed ofindividual memory banks one or more of which may have dedicated controlsignal lines.

In operation, a RF signal is received through the receive part of thetag's transceiver that contains the instruction to adjust the tag forits environment. The processing block 944 interprets the command andsends one or more signals over appropriate control signal lines toeffect the adjustment (e.g., processing block sends a signal overcontrol signal line 960 if the demodulator 942 is to be adjusted).

For illustrative ease, FIG. 9A does not depict other specificsub-circuits whose operation can be changed to effect an environmentallybased adjustment. Examples of such sub-circuits include an oscillator, arectifier circuit (which may be presumed to be within PMU 941), ananalog random number generator, a digital random number generator,encryption/decryption logic, charge pump circuitry (e.g., within writecircuitry of memory 950) and sense amplifier circuitry (e.g., withinread circuitry of memory 950). Although not depicted, each suchsub-circuit may have its own dedicated control signal line from theprocessing block 944 consistent with the architectural approach observedin FIG. 9A.

As alluded to above, the specific change made to a sub-circuit mayinclude at least one of: i) turning the sub-circuit on; ii) turning thesub-circuit off; iii) altering a voltage bias of the sub-circuit; iv)altering a current bias of the sub-circuit; and, v) altering a thresholdof the sub-circuit. Enablement/disablement circuitry can be coupled to acontrol signal line to turn a sub-circuit on/off. For example,enablement/disablement circuitry can be coupled to memory control signalline 990 to turn memory 950 (or a memory bank of memory 950) on/off.Enablement/disablement circuitry can be, for example, circuitry designedto connect/cutoff any of a sub-circuit's power supply voltage, a clocksignal that is fed to the sub-circuit, or an input signal that isprovided to the sub-circuit.

With respect to bias adjustments, generally, a sub-circuit can be viewedas an arrangement of transistors that are interconnected so as toperform the sub-circuit's function. The arrangement of transistors canbe viewed as having a substantially time invariant (e.g., “DC”)operating point that corresponds to the nominal bias of the circuit whena power supply voltage is supplied to it. For instance, for a givensupply voltage, the nominal bias may be the DC voltages that appear atvarious nodes in the sub-circuit and DC currents that flow throughspecific current paths in the sub-circuit. When a time-varying signal isprovided at an input to the sub-circuit, the voltages and currents mayswing or otherwise deviate from these bias points.

Adjustment of a voltage and/or current bias within a sub-circuit may beundertaken, for example, to change a fundamental operating property of asub-circuit. For instance, by changing a voltage and/or current biaswithin a sense amp, the gain of the sense amp may be made to change.Likewise, changing a voltage and/or current bias within an oscillatorcan cause an oscillator to change its oscillation frequency. As just onemore example, a bias voltage and/or bias current change may be appliedto a random number generator circuit to change the randomness of itsoutput.

A threshold may also be adjusted within a sub-circuit. For instance, forsub-circuits that make binary decisions, a threshold may be changed toadjust the level at which the sub-circuit decides a signal correspondsto a “1” or a “0”. As just a few examples, the demodulator 942 or asense amplifier within a memory bank may have an internal thresholdlevel changed to a higher value in the presence of a noisy environment(or lowered in the presence of a quiet environment). Generally, anycircuit can be made to change some principle or feature of its operationby changing its voltage bias, current bias and/or a threshold within thesub-circuit. Voltage bias adjustment circuitry, current bias adjustmentcircuitry and/or threshold adjustment circuitry may include one or moretransistors that are coupled to a bias point or threshold circuit anddesigned to impart a change thereto.

FIG. 9B shows another tag design which concentrates at least some of thecircuitry that puts into effect an environmentally based adjustment intothe PMU. For instance, for those environmentally based adjustments thatrequire a sub-circuit's supply voltage to be adjusted, the PMU may beinvoked to make the change. In this case, for example, the processingblock interprets the received instruction and sends a command to PMUalong control signal line 971. The PMU receives and interprets thecontrol signal from line 971 and adjusts the supply voltage of theindicated sub-circuits. For example, the supply voltage of thedemodulator and modulator can be changed, connected or cutoff alongcontrol signal lines 972 and 973, respectively. The supply voltages ofany of the other sub-circuits could be controlled in this manner.Conceivably, bias or threshold adjustments could also be effected fromthe PMU.

FIG. 9C depicts a tag embodiment showing each of the sub-circuitsmentioned above whose operation is capable of being adjusted in responseto receipt of an instruction that was determined based on a sensedaspect of an environment. For ease of drawing, other tag components(such as the antennas and various interconnections) have been omitted.FIG. 9C shows a pair of demodulators 945, 946 having respective controlsignal lines 961, 962. As discussed above, a sensed environmental aspectmay trigger dual mode demodulation (in which case both demodulators 945,946 are enabled) or single mode demodulation (in which case one of thedemodulators may be enabled and the other disabled).

FIG. 9C also shows a rectifier 983 that may, for example, beenabled/disabled and/or have its power conversion efficiency adjustedthrough control signal line 963. A modulator 946 is also shown that maybe enabled/disabled and/or have its modulation response adjusted throughcontrol signal line 964. The operation of random number generator 981and encryption/decryption logic 982 may also be respectively adjusted(e.g., enabled/disabled) through control signal lines 965 and 966. Senseamplifier 951 and charge pump 952 are associated with memory/memory bank950 and may be adjusted (e.g., by changing their respective gains) inany of the ways discussed above. Likewise, oscillator 980 may beadjusted (e.g., by changing its oscillation frequency) through controlsignal line 968. FIG. 9C adopts the approach of FIG. 9A in which thecontrol signal lines 961-968 flow from the processing block 944.Alternatively, completely or partially, the approach of FIG. 9B may beadopted in which the PMU 941 provides control signals over correspondingcontrol lines to various sub-circuits.

Environmentally based instructions are preferably sent to one or moretags according to Tune command format. As described in previously filedU.S. patent application Ser. No. 12/112,699, filed Apr. 30, 2008, a Tunecommand can be used to encode a specific instruction.

The Tune command can be implemented as a custom command that is notspecified in a particular communication protocol (e.g., Gen2), and, madeby a sequence of bits chosen so that they do not conflict with othercommands of the protocol. Here, a specific environmentally driveninstruction to perform one or more specific acts to one or more of atag's sub-circuits can be implemented as a command with a custom payloadwhere the payload is used to distinguish among different custom commands(e.g., different environmentally driven specific acts to be performed),and, further transfer a parameter for the commands (e.g., the specificone or more sub-circuits to which a custom command is to be applied).

The section in the payload used for carrying Tune formatted instructionscan be a mask field, according to embodiments. For the Gen2 Spec, twosuch Gen2 commands that can transport a Tune formatted custom commandare the Select command and the BlockWrite command. Between these twocandidate commands, it should be considered that the Select command canbe transmitted before or after a tag is singulated out of itspopulation, while the BlockWrite is better suited for singulated tags.In addition, the BlockWrite command is optional to the Gen2 Spec, andthe tag would probably have to have a controller that can accept it.

Each one of the custom commands can thus be constructed as animplementation of this Select command or the BlockWrite command. Anexample is now described in terms of the Select command, but would applyequally to the BlockWrite command. Furthermore, embodiments are notlimited to the Tune command or its derivatives described here. A commandcarrying instructions for different environmentally driven specific actsto be performed by tag circuits may be formatted and/or nameddifferently than the specific Tune command discussed herein.

FIG. 10A is a table illustrating the fields of the Select command of theGen2 Spec. Version 1.1.0 of the Gen2 Spec is hereby incorporated byreference in its entirety. The fields of this Select command areexplained in more detail in the above mentioned Gen2 Spec. In addition,the implementation of this Select command can have a custom payload sothat it operates as a Tune formatted command.

FIG. 10B is a table illustrating how a number of custom commands can beenabled in a reader and a tag. EBV stands for Extensible Bit Vector. TheMask Field can be partitioned as shown, into two primary subfields,named FEF and FCF.

The Feature Enabling Field (FEF) enables the tag to verify that it is aproper recipient for the command, by comparing the transmitted FEF valueagainst a value in Membank. In this case, Membank can be EPC, TID orUSER memory. As can be seen, the FEF can be further partitioned intosubfields for better clarity. Such subfields might include, for exampleif Membank is TID memory as described in Gen2 v1.1.0, a ClassIdentifier, the MDID, and an Indicator Bit.

The Class Identifier can be two bits. For example, EPCglobal cancorrespond to a value of 10. This would allow the custom command toapply, for example, only to EPCglobal tags.

The MDID is the tag manufacturer's ID, which is stored in the tag's TIDmemory. For Impinj tags, this number is 000000000001 or 100000000001.The MDID allows a reader to select tags of only the manufacturer ofinterest. So, even if this Select command is transmitted and receivedbefore singulation, the Select command can select also according to thetag manufacturer's ID. This will cause the manufacturer's tags to beselected, and thus the reader can ensure prior knowledge of the tagmanufacturer's identification.

The Indicator Bit can be set to 0 or 1. In the Gen2 spec, a tag modelnumber follows the MDID. A bit of this model number can serve as theIndicator Bit, and can be interpreted as follows: If it is 0, the tagscan interpret the command as an “ordinary” Select, and execute it perthe Gen2 spec. Else, if it is 1, the tags can interpret the Selectcommand as a custom instruction, and execute according to the FCF.

The Feature Command Field (FCF) can have a command code that indicatesthe number of the custom command. For example, a command code of 00000could be a first custom command. A 5-bit field permits 32 possiblecustom commands. A command code of 11111 could indicate an extendedcommand field that extends into the subsequent data field, allowing morethan 32 custom commands. The data field can also contain data needed toimplement the custom instruction and its meaning will derive from thecommand code. For example, the sub-circuit identifier of the Tunecommand can be encoded as data in the FCF subfield shown in FIG. 10.

Thus, a Tune formatted command corresponds to a custom instructionhaving a command code portion (e.g., as in the first part of the FCFfield) and a data portion (e.g., as in the second part of the FCFfield). Thus, for instance, the environmentally driven custom commandcode could be embedded in the first part of the FCF field and beinterpreted as any one or more of: turn a sub-circuit on, turn asub-circuit off, adjust a sub-circuit voltage bias, adjust a sub-circuitcurrent bias, or adjust a sub-circuit threshold. The specificsub-circuit or set of sub-circuits to which the command code specifiedin the first portion are to be applied to may be identified in thesecond, data portion.

In some embodiments, the tag may ignore the Target and Action field inthe Select command, depending on whether these fields are relevant. Inother embodiments, the tag may also set the appropriate Target flag.

In preferred embodiments, the entire Select command must be valid forthe tag to accept and execute the custom command. That means validvalues for Membank, Length, Pointer, Mask, CRC-16, etc.

Numerous details have been set forth in this description, which is to betaken as a whole, to provide a more thorough understanding of theinvention. In other instances, well-known features have not beendescribed in detail, so as to not obscure unnecessarily the invention.

The invention includes combinations and subcombinations of the variouselements, features, functions and/or properties disclosed herein. Thefollowing claims define certain combinations and subcombinations, whichare regarded as novel and non-obvious. Additional claims for othercombinations and subcombinations of features, functions, elements and/orproperties may be presented in this or a related document.

The invention claimed is:
 1. A method of adjusting operation of an RFIDtag for an environment, the method comprising: receiving an inputassociated with a sensed aspect of the environment, the input selectedfrom the set of: an expected number of RFID tags within the environment;a velocity of the RFID tag; electromagnetic noise within theenvironment; presence of one or more RFID readers within theenvironment; humidity within the environment; temperature within theenvironment; and an electromagnetic reflection property of theenvironment; sending an instruction to the RFID tag based on the input,the instruction encoded in a TUNE command and causing the RFID tag toperform one of the following: turning a sub-circuit of the RFID tag'ssemiconductor chip on; turning a sub-circuit of the RFID tag'ssemiconductor chip off; altering a bias current within a sub-circuit ofthe RFID tag's semiconductor chip; altering a bias voltage within asub-circuit of the RFID tag's semiconductor chip; and, adjusting athreshold within a sub-circuit of the RFID tag's semiconductor chip. 2.The method of claim 1 wherein the sub-circuit includes at least one fromthe set of: a random number generator circuit; a demodulator receivepath circuit; a nonvolatile memory bank circuit; a modulator circuit; anencryption/decryption circuit; an oscillator circuit; a sense amplifiercircuit; a rectifier circuit; and a charge pump circuit.
 3. The methodof claim 1 wherein the receiving and sending are performed by an RFIDreader.
 4. The method of claim 1 wherein the method further comprises acontroller performing the following: determining the instruction basedon the sensed aspect of the environment; sending the instruction to anRFID reader for transmission to the RFID tag.
 5. A Radio FrequencyIdentification (RFID) reader configured to communicate with an RFID tag,the reader comprising: an input configured to receive an instructionbased on a sensed aspect of an environment encompassing the RFID tag; aprocessor block arranged to: encode the instruction in a TUNE command,cause the RFID tag to perform one of the following: turn a sub-circuitof the RFID tag's semiconductor chip on; turn a sub-circuit of the RFIDtag's semiconductor chip off; alter a bias current within a sub-circuitof the RFID tag's semiconductor chip; alter a bias voltage within asub-circuit of the RFID tag's semiconductor chip; adjust a thresholdwithin a sub-circuit of the RFID tag's semiconductor chip; and, atransceiver arranged to transmit the encoded instruction to the RFIDtag.
 6. The RFID reader of claim 5 wherein the RFID reader furthercomprises environmental sensing circuitry to sense the aspect of theenvironment.
 7. The RFID reader of claim 6 wherein the environmentalsensing circuitry comprises a receiver to perform at least one of: senseelectromagnetic noise within the environment; sense the presence of oneor more RFID readers within the environment; sense an electromagneticreflection property of the environment; sense an expected number of RFIDtags within the environment; and sense a velocity of the RFID tag. 8.The RFID reader of claim 6 wherein the environmental sensing circuitrycomprises at least one of: a humidity detector to sense humidity withinthe environment; a temperature detector circuitry to detect temperaturewithin the environment.
 9. A method of adjusting an operation of an RFIDtag for an environment, the method comprising: sensing an aspect of theenvironment; supplying the sensed aspect to an RFID reader; sending aninstruction based on the sensed aspect from the RFID reader to the RFIDtag, the instruction encoded in a TUNE command and causing the RFID tagto perform one of the following: turning a sub-circuit of the RFID tag'ssemiconductor chip on; turning a sub-circuit of the RFID tag'ssemiconductor chip off; altering a bias current within a sub-circuit ofthe RFID tag's semiconductor chip; altering a bias voltage within asub-circuit of the RFID tag's semiconductor chip; and, adjusting athreshold within a sub-circuit of the RFID tag's semiconductor chip. 10.The method of claim 9 wherein the sensed aspect of the environmentincludes at least one from a set of: electromagnetic noise within theenvironment; presence of one or more RFID readers within theenvironment; humidity within the environment; temperature within theenvironment; an electromagnetic reflection property of the environment;an expected number of RFID tags within the environment; and a velocityof the RFID tag.
 11. The method of claim 9 wherein the sub-circuitincludes at least one from the set of: a random number generatorcircuit; a demodulator receive path circuit; a nonvolatile memory bankcircuit; a modulator circuit; an encryption/decryption circuit; anoscillator circuit; a sense amplifier circuit; a rectifier circuit; anda charge pump circuit.
 12. The method of claim 9 wherein the sensing isperformed by another RFID reader.
 13. The method of claim 9 wherein themethod further comprises a controller performing the following:determining the instruction; and sending the instruction to the RFIDreader.